A display device which emits an image to an observer, such as a liquid crystal display, a plasma display, a rear projection, an organic EL, or an FED, includes an image source and an optical sheet including a layer having various functions for improving the quality of image light from the image source and emitting the light to the observer.
An example of the optical sheet is disclosed in Patent Document 1. The optical sheet described in Patent Document 1 has portions for transmitting image light and a triangular structure disposed therebetween. Then, the sheet reflects image light at an interface between the portions for transmitting image light and the triangular structure to disperse the light. This configuration can allow the image light to be dispersed at a large angle.